As is well known, a widely used conventional linear bearing is of ball bush type. This type of linear bearing can carry a vertical load satisfactorily, but when a moment load or upward is applied thereon, it functions only by a fraction of vertical load carrying capability.
To obviate the drawback with the conventional linear bearing as described above, the inventors developed a linear bearing with a retainer incorporated therein which contains a plurality of longitudinally extending ball arrangements located in a symmetrical relation and side covers firmly secured to both end faces of the bearing body, said side covers having an U-shaped concave portion located in alignment with said plural ball arrangements so as to reverse the direction of movement of the loading balls.
However, it is found that the newly developed linear bearing has a bottleneck that it is difficult to manufacture this type of linear bearing at an inexpensive cost, because when it is required to change the length of the bearing body the retainer should be prepared which has its length changed in proportion to the modified bearing body.